1. Field of the Invention
The invention relates to a continuous printing machine and in particular to a machine for typographical printing. These machines in general comprise a number of printing units in series, each of which is fitted with a plate or cliche carrying roller which, rolling on a counterpressure roller, called print roller, transfers the image from the inked cliche to a ribbon of paper or other material fed between the two aforementioned rollers. The cliche carriyng roller is in turn inked by at least another roller called inking roller, having a surface in an at least partially absorbent material to draw ink from a source of it and continuously transfer the same, via one or more distribution rollers, to the cliche carrying roller.
For high quality printing, it is imperative that the quantity of ink transferred from the inking roller or rollers to the cliche carrying roller be perfectly regulated; if too much ink is transferred to the cliche carrying roller, then some areas would be inked which should not be, and if too little ink is transferred, there would be areas without ink which should have been inked. In order to regulate this supply, the cliche carrying roller is fitted on one or preferably both sides with reference disks having a constant diameter equal to the diameter of the cliche carrying roller when a cliche is ftted thereon. Likewise, one or preferably two cams are coupled to each inking roller, said cams being integral with the axis of the inking roller but do not rotating with it; these cams can be registered in position with reference to the disks on the cliche carrying roller to determine the correct pressure between the two roller in operation. The setting of this cams is very critical and requires skilled personnel and a lot of time to carry out correctly.
In the most recent typographic printing machines the structure of the machine, or rather of each printing unit, is such as to enable the cliche carrying roller to be substituted by rollers with different diameters depending on the formats to be printed. The cliche carrying rollers are substituted while the position and size of the print or counterpressure roller remains constant, in such a manner that the axis of the cliche carrying roller moves closer or further away from the print roller axis, depending on whether the substituting cliche carrying roller has a smaller or larger diameter.
It is obvious that, when changing the cliche carrying roller size, the inking roller or rollers must be able to always work in contact with the cliche carrying roller, and accordingly to work with all cliche carrying roller that can be fitted. For that reason, the inking rollers are fitted in a mobile way within different possible positions by moving their axes along an arc of a circle so that they approach or depart the area where the cliche carrying roller lies, until they make contact with its surface. Moreover, since the inking rollers move along an arc of a circle centered on a rotation axis in the frame of the machine to keep in contact with the surface of the cliche carrying roller each time the latter is substituted on a printing unit, then the cam or pair of cams associated with each inking roller move in a similar way along an arc having the same center. When, at the end of its rotation, the cam is into contact with the disk on the new cliche carrying roller, the point of contact between the inking roller cam and the cliche carrying roller disk is no longer the same as the original setup. If printing were proceeded with under these conditions, as the original registration is changed, the ink supply would be incorrect, either too much or too little being delivered. Accordingly, at every change of format of the cliche carrying roller it is necessary to reset the inking roller cam to get optimum inking. Such a reset would take up capacity, personnel, time etc.